confluence_3-29-087503/31/08 - The Clark Fork and Blackfoot Rivers flowed freely for the first time in a century when the cofferdam around the old powerhouse site was breached Friday.

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March 26, 2008

Coffer dam
Cofferdam

This week the temporary earthen cofferdam that protects the old powerhouse area will be breached, freeing river flow at the confluence of the Clark Fork and Blackfoot Rivers for the first time in 100 years.

The event is scheduled for Friday March 28th at 11:30 a.m. To observe this historic event, the EPA and agencies are encouraging the public to use the Milltown bluff overlooking the Dam and the confluence. See the attached map (PDF) for directions to the bluff. The breach can also be seen via the Dam Cam.

Here’s the sequence of events leading up to this momentous event. First, the Clark Fork River was routed into the bypass channel along I-90 during the week of March 17th.

The temporary earthen cofferdam that has kept the powerhouse area dry will be dug out as much as possible. The steel sheet-piling around it has already been removed. Upstream of the old powerhouse area, a pilot channel is being dug that leads from the cofferdam toward the Blackfoot River.

On Friday, the cofferdam will be notched, and then the level of the reservoir will be raised by closing the radial gate on the dam. When the water rises it will start to flow down the pilot channel toward the cofferdam. As the remains of the cofferdam wash away, the flow of both rivers will spill through this channel, lowering the level of the reservoir by another 12-14 feet.

When the cofferdam breaches, there will be a surge of both water and sediment. Expect to see a very muddy river when this happens, especially near the dam. And as the reservoir drains, the water level in the river below will temporarily rise. The surge of water is expected to be about 4 feet high immediately below the dam, 3.3 feet near Pinegrove, 1.5 feet through most of Missoula, and down to six inches by the time it hits the Bitterroot. The expected surge will hit Missoula about one and a half hours after the dam is breached. (See the attached map.)

The surge won’t really look like a wave – the river will simply rise and fall with a big pulse of muddy water – but river users should be aware that this is happening. EPA is urging people to stay off the river on the 28th, because there may be debris (such as logs) that wash downstream, and they would be hard to see in the muddy water.
For more on the powerhouse removal, see CFRTAC’s Dam News 2008 (PDF) or the EPA press release (PDF).

March 26, 2008

CFRTAC volunteer Pat Munday delivered a Montana Public Radio Commentary that looks at the recent release of the Consent Decree for the upper Clark Fork River cleanup and the need for comprehensive planning in the watershed. Read it here (PDF).

Outlet Equipment03/20/08 - Some amazing work is going on at the Milltown Reservoir Sediments Superfund site. The bypass channel for the Clark Fork River River is nearly open for business.

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March 20, 2008

The Natural Resource Damage Program (NRDP) has released a Draft Conceptual Framework for an Upper Clark Fork River Basin Restoration Priorities Road Map (PDF). This document outlines the proposed conceptual framework for how the Upper Clark Fork River Basin (UCFRB) Restoration Fund would be prioritized via earmarking after settlement of the natural resource damage litigation. The agency is seeking public comment through April 8. More information is available at the NRDP website.

March 19, 2008

The Montana Natural Resource Damage Program is looking for feedback on its newly released draft final “State Restoration Monitoring and Maintenance Plan for the Restoration Plan for the Clark Fork River and Blackfoot River near Milltown Dam" (PDF). This draft document, under review by the EPA and DEQ, has two monitoring components: one for monitoring State activities stated in the Milltown Consent Decree and a second for monitoring “critieria” established by the State to monitor the success of the restoration activities. The State is looking for comments on this document by April 24, 2008.

Please address all comments to Doug Martin (This email address is being protected from spambots. You need JavaScript enabled to view it.) at the address listed below or electronically.

NRDP/DOJ
PO Box 2011425
Helena, MT 59620-1425

March 17, 2008

Confluence and bypass channel
Confluence and bypass channel

Yet another major project milestone will be passed this week when the Clark Fork River is diverted into the bypass channel. According to the EPA, on Tuesday March 18 the berm at the outlet will be breached, allowing water from the Blackfoot to backfill the bypass channnel. Next week, the inlet will be opened, fully diverting the Clark Fork River around contaminated sediments and into the channel. The bypass channel is a key measure to reduce downstream impacts. For details, see the EPA press release,
the EPA’s weekly update (PDF) or coverage in the Missoulian.

March 17, 2008

The Montana Dept. of Transportation warns that removal of the center pier of the old Highway 200 bridge in Milltown may lead to some traffic delays of up to a half hour this week.  The bridge is being replaced as part of a mitigation effort related to the Milltown Superfund project. Read the MDT press release after the jump.

FOR IMMEDIATE RELEASE

For more information:
Charity Watt Levis, (406) 444-7205

Expect traffic delays over Milltown bridge next week, MDT advises

The Montana Department of Transportation would like to inform motorist that the Highway 200 bridge located over the Blackfoot River in Milltown will be closed for a short time during the next week.  MDT will provide 24-hours notice prior to the closure.  The closure is expected to last up to 30 minutes.

MDT will be removing the center pier of the old bridge.  For safety reason, the new bridge will be closed to traffic while removal activities commence.  Scheduling of the removal is dependent on weather and other construction activities.

MDT is committed to expediting this project and apologizes for any
inconveniences this work may cause.   For the latest construction and weather reports, please dial 511 or visit www.mdt511.com

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